This common annoyance can be easily prevented
By Phil O'Keefe
A fairly common issue with some guitar bridge parts is rattling. As the instrument is played, it resonates. These vibrations are important to the sound of the instrument, but there can be unfortunate and un-wanted side effects. Other parts of the instrument can sympathetically resonate and vibrate, which can cause those parts to work themselves loose. Once that happens, all sorts of other bad things can occur, such as rattles and buzzes. This is a fairly common issue with Jaguar and Jazzmaster bridges, but it can occur with any metal saddle height or intonation adjustment screws.
Maybe you have a nut on a guitar or pedal output jack, or on your Strap Locks that keeps coming loose. Or maybe the problem is with a set-screw on a volume knob or tone control that regularly works itself loose. These are also very common problems.
How do you stop this from happening? One of the best ways I've found is to put a small drop of Loctite thread locker (Fig 1) on the parts. The important thing is to use the correct type - ALWAYS use "blue" Loctite and NEVER use red! Red locks the threads together permanently, which you definitely do not want - you want to be able to still adjust things later if needed. The Loctite Blue 242 formula will hold things fast, but the parts can still be disassembled with normal hand tools.
Figure 1: Loctite Blue 242 thread locker
To use the Loctite on bridge parts, make sure the parts are clean and dry and that you have them set the way you want them, then apply a small drop to the two joined parts where they connect. The liquid will flow into the tiny spaces between the two metal parts and cures in the absence of air. On larger parts, you can apply it directly to the threads, then assemble and tighten them. It sets up in about ten minutes, but I normally leave the guitar alone for a day to make sure it's completely locked down. On larger surfaces, such as output jack nuts, you may need to use a few drops to make sure it stays put.
A word of caution - Loctite should not be used on plastic parts, as it can cause them to crack. It is intended for use on metal parts only.